1. Field Of The Invention
The present invention relates to a method and device for detecting shifts in wind direction on a floating, anchored vessel.
2. Description Of The Prior Art
In the conventional practice of commercial gill net fishing, a gill net is set in the sea overnight from a fishing boat, and the fishing boat is anchored, relative to the net, at the downwind end of the net. The net thereby serves as a floating sea anchor.
It is not uncommon for a maritime wind to shift at night, particularly in the vicinity of a land mass. Such wind shifts typically occur very late at night. When the wind significantly shifts in direction, a fishing boat anchored to a net can frequently be blown by the shifting wind back into the net. When this happens there is a considerable likelihood that the fishing boat will foul the net. Also, the fishing boat, blown by a shifting wind, is likely to be blown into the net float line. The net float line is then likely to become fouled in the boat propeller or rudder and the net can collapse, thereby becoming knotted and tangled.
Commercial gill fishing nets are typically about 6,000 feet long and extend to a depth of about 150 feet. Tangles and tears in the net and the net line typically require from hours to weeks of work to recover the net and to repair it.
The present practice in commercial drift net fishing is either to have some crew member stand watch all night to keep track of the position of the boat relative to the net, or to set an alarm which sounds every hour or so. In either event, one or more of the crew is deprived of adequate rest. This leads to inefficiency in the daytime work of commercial gill fishing. Also, the repetitive sounding of an alarm when no wind shift has occurred sometimes leads to complacency and can result in an inadequate assessment of wind conditions with each sounding of the alarm.